Question

Copper sulfate, when it is dissolved in water, has a blue color. When steel wool is mixed with a copper sulfate solution, the steel wool disappears, a brownish solid forms, and the color of the solution changes from blue to green.
Choose one answer that gives the best evidence that a chemical reaction took place.

A. The color change from blue to green happens in nature.

B. The disappearance of the steel wool shows that a new substance has formed.

C. The solid precipitate is a waste product in the reaction.

D. Energy is lost in this reaction like all other reactions.


Which answer did you choose? Explain your reasoning.

Answer 1

Answer:

A. The color change from blue to green happens in nature.

Explanation:

The color change is an indicator of a chemical reaction that has occurred. Although color changes are not necessarily good diagnostic tool to measure if a chemical reaction has occurred or not.

• In this reaction, color changes is quite an effective tool
• Chemical changes usually involves the formation of a new product from the chemical reaction.
• Also, the steps are not easily reversible.
• For this reaction, color change is the most appropriate signal for a chemical change.